饱和黏土不排水剪切特性及双曲线模型
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摘要
采用真空抽吸制样技术制备的饱和重塑黏土,在0.015～3.75%/min应变速率范围内进行了多组不固结不排水(UU)剪切试验。通过对试验结果的分析,着重探讨了应变速率和约束压力对应力-应变关系及其强度特性的影响。试验结果表明,黏土的应力-应变关系与强度特性基本上不依赖于约束压力,而受应变速率的影响较为显著,强度随应变速率的增加而增长,增长幅度可达70%,通过对数据的归一化,采用线性拟和建立了不排水强度与应变速率之间的经验关系。进而考虑应变速率对不固结不排水应力-应变关系的影响,对双曲线非线性本构模型进行了研究,详细介绍了模型参数的确定方法,并分别采用静力三轴和扭剪试验结果对模型进行了验证。
A series of unconsolidated-undrained(UU) triaxial tests are performed in order to examine the effect of strain rate and confining pressure on strength and stress-strain behavior of reconstituted saturated clays.Strain rate is controlled to vary between 0.015 %/min and 3.75 %/min.It is found by comparing the experimental data that strength and stress-strain behavior are mainly affected by strain rate,however,they are almost independent on confining pressure.Undrained shear strength of the saturated clay increases with increase of strain rate;and the increase of 70 % of strength may be attained.An empirical correlation between strength and strain rate is proposed after a given normalization.Furthermore,the hyperbolic constitutive model of nonlinearity is recommended in order to take the effect of strain rate on the stress-strain relation into consideration;and the experimentally-based procedure for defining the parameters in the hyperbolic model is given.The model is verified through test data in the monotonic triaxial and torsional shear tests.
A series of unconsolidated-undrained(UU) triaxial tests are performed in order to examine the effect of strain rate and confining pressure on strength and stress-strain behavior of reconstituted saturated clays.Strain rate is controlled to vary between 0.015 %/min and 3.75 %/min.It is found by comparing the experimental data that strength and stress-strain behavior are mainly affected by strain rate,however,they are almost independent on confining pressure.Undrained shear strength of the saturated clay increases with increase of strain rate;and the increase of 70 % of strength may be attained.An empirical correlation between strength and strain rate is proposed after a given normalization.Furthermore,the hyperbolic constitutive model of nonlinearity is recommended in order to take the effect of strain rate on the stress-strain relation into consideration;and the experimentally-based procedure for defining the parameters in the hyperbolic model is given.The model is verified through test data in the monotonic triaxial and torsional shear tests.
引文
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[2]SHEAHAN T C,LADD C C,GERMAINE J T.Rate-dependent undrained shear behavior of saturated clay[J].Journal of Geotechnical Engineering,ASCE,1996,122(2):99-108.
[3]蔡羽,孔令伟,郭爱国,等.剪应变率对湛江强结构性黏土力学性状的影响[J].岩土力学,2006,27(8):1 235-1 240.CAI Yu,KONG Ling-wei,GUO Ai-guo,et al.Effects of shear strain rate on mechanical behavior Zhanjiang strong structured clay[J].Rock and Soil Mechanics,2006,27(8):1 235-1 240.
[4]沈珠江.理论土力学[M].北京:中国水利水电出版社,2000.
[5]ANDERSEN K H,LAURITZSEN R.Bearing capacity for foundations with cyclic loads[J].Journal of Geotechnical Engineering,ASCE,1988,114(5):540-555.
[6]齐剑峰,聂影,赵维,等.室内黏土试样制备技术的改进及应用[C]//土工测试技术实践与发展论文集(第24届全国土工测试学术研讨会.)郑州:黄河水利出版社,2005:123-126.
[7]DUNCAN J M,CHANG C Y.Nonlinear analysis of stress and strain in soils[J].Journal of the Soil Mechanics and Foundation Divisions,ASCE,1970,96(SM5):1 629-1 653.
[8]MARTIN P P,SEED H B.One-dimensional dynamic ground response analysis[J].Journal of the Ge-otechnical Engineering Division,ASCE,1982,108(7):935-954.
[9]陈国兴,谢君斐,张克绪.土的动模量和阻尼比的经验估计[J].地震工程与工程振动,1995,15(1):73-84.CHEN Guo-xing,XIE Jun-fei,ZHANG Ke-xu.The empirical evaluation of soil moduli and damping ratio for dynamic analysis[J].Earthquake Engineering and Engineering Vibration,1995,15(1):73-84.
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